feat(connectors): use TCP client for Flink sink

[Standing-Man]

Which issue does this PR address?

• Closes Flink connector - transport - http to tcp #2484.

Rationale

The Flink connector used different transports for reading and writing messages. The source already used the native TCP client, while the sink sent messages through the HTTP client and hardcoded the HTTP port to 3000.

This caused the same IggyConnectionConfig to behave differently between the source and sink. It also required deployments to expose the HTTP API even when the configured Iggy endpoint used the TCP port.

The source and sink also parsed server addresses independently. The source relied on splitting the address by :, while the sink used URI parsing. This produced inconsistent behavior and did not reliably support IPv6 or validate malformed endpoints.

What changed?

• Replaced IggyHttpClient with the blocking IggyTcpClient in the Flink sink.
• Configured the TCP client using the existing connection settings:server host and port
  • username and password
  • connection and request timeouts
  • retry count and backoff
  • TLS
• Updated IggySinkWriter to send messages through TCP.
• Updated sink shutdown to flush pending messages and close the TCP client, while preserving both flush and close failures.
• Added a shared TcpEndpoint parser used by both the Flink source and sink.
• Added support for:host-only addresses using the default TCP port 8090
  • host:port
  • tcp://host:port
  • bracketed IPv6 addresses
• Added validation for unsupported schemes, missing hosts, invalid ports, and addresses containing user info, paths, queries, or fragments.
• Added unit tests covering valid and invalid TCP endpoint formats.
• Ignored Gradle-generated .kotlin cache directories.

Local Execution

• Passed / not passed
  Passed
• Pre-commit hooks ran / not ran
  Ran

AI Usage

[github-actions]

Thanks for the PR. It is labeled S-waiting-on-review and queued for review.

Slash commands (own line, regular comment) move it around the queue:

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See CONTRIBUTING.md for details.

[codecov]

Codecov Report

❌ Patch coverage is 41.93548% with 36 lines in your changes missing coverage. Please review.
✅ Project coverage is 74.02%. Comparing base (313c50b) to head (4f54771).

Files with missing lines	Patch %	Lines
...ache/iggy/connector/flink/sink/IggySinkWriter.java	0.00%	17 Missing ⚠️
...org/apache/iggy/connector/flink/sink/IggySink.java	0.00%	13 Missing ⚠️
.../org/apache/iggy/connector/config/TcpEndpoint.java	89.65%	2 Missing and 1 partial ⚠️
...apache/iggy/connector/flink/source/IggySource.java	0.00%	3 Missing ⚠️

❌ Your patch check has failed because the patch coverage (41.93%) is below the target coverage (50.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #3657      +/-   ##
============================================
+ Coverage     73.98%   74.02%   +0.04%     
- Complexity      937      956      +19     
============================================
  Files          1301     1301              
  Lines        147354   147239     -115     
  Branches     122911   122768     -143     
============================================
- Hits         109013   108990      -23     
+ Misses        34868    34777      -91     
+ Partials       3473     3472       -1     

Components	Coverage Δ
Rust Core	74.32% <ø> (+0.04%)	⬆️
Java SDK	62.59% <41.93%> (+0.14%)	⬆️
C# SDK	72.12% <ø> (-0.07%)	⬇️
Python SDK	92.17% <ø> (ø)
PHP SDK	84.29% <ø> (ø)
Node SDK	91.35% <ø> (+0.09%)	⬆️
Go SDK	42.71% <ø> (ø)

Files with missing lines	Coverage Δ
.../org/apache/iggy/connector/config/TcpEndpoint.java	89.65% <89.65%> (ø)
...apache/iggy/connector/flink/source/IggySource.java	0.00% <0.00%> (ø)
...org/apache/iggy/connector/flink/sink/IggySink.java	0.00% <0.00%> (ø)
...ache/iggy/connector/flink/sink/IggySinkWriter.java	0.00% <0.00%> (ø)

... and 12 files with indirect coverage changes

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[hubcio]

@mmodzelewski and also please check this one :)